How can I get the color in the middle of a face using Python?
In the middle of a face is an average color of all the vertices. For triangle this means:

Col_RGB = ((R1+R2+R3)/3, (G1+G2+G3)/3, (B1+B2+B3)/3)

Where each vert has color in form of (Rn, Gn, Bn) for n in (1..3).